MST1 and small cell lung carcinoma: For example, PP2A dephosphorylates macrophage stimulatory protein (MST1/2) and activates Yes‐Associated Protein (YAP), leading to tumor growth;[55] it has also been found that PP2A with the B55α subunit stabilizes MYC, promoting tumor growth.[56] Our findings reveal that PP2A dephosphorylates PKCζ, contributing to CSLC expansion in MUC1‐positive SCLC.